Exchange-traded funds are undergoing a bit of a renaissance, with new styles of indexing. How smart is smart beta?

Most of us range from fairly skeptical to deeply suspicious of any marketing terminology when it comes to buying cars or homes or Google Glass. But that doesn't stop Wall Street from peddling one elixir after another, wrapped in academic research and carefully worded nonpromises. The latest? Smart beta, an umbrella term for index investing designed to beat...